The CRPRC has developed a breeding colony of rhesus macaques free of the following specific pathogens Herpes B, Type D retrovirus (SRV), Simian Immunodeficiency Virus (SIV), and Simian T Cell Lymphotrophic Virus (SLTV). The aims of this colony are 1) To make available for researchers a colony of rhesus macaques free of these specific pathogens, in order to minimize undesirable variables in the research model. 2) To develop a long term breeding colony of rhesus macaques free of these specific pathogens in order to minimize occupational health risks. Rhesus infants are weaned from their dams directly to our SPF facility at approximately six months of age. The infants are pair housed indoors for the first 8 months in the program. Strict infection control procedures are employed to prevent transmittal of pathogens between pairs. During this 8 months, infants are tested intensively for the viral agents of concern (see attached testing schedule). Animals negative by both antibody and viral assay are maintained in the SPF colony. Animals with positive viral tests (and cage mates) are immediately removed from the SPF colony, returning to the standard CRPRC weaning program. After the first 8 months, remaining animals are moved to outdoor (corncrib) housing and maintained in groups of 10-15. The animals continue to be tested biannually to confirm negative viral status. Currently 105 animals are in the CRPRC SPF colony. The program was established in 1993. Animals are added to the colony each breeding season. Currently there are 22 animals housed in the indoor colony and 43 animals in corncribs. An outdoor SPF breeding colony was established in North Corral 1 in 1995, and contains 40 animals.